Radioactive iodine ablation (I-131) therapy

We use radioactive iodine ablation (I-131) therapy to treat papillary and follicular thyroid cancers, and thyroid cancer that has spread to the lymph nodes and other parts of the body.

The treatment destroys, or ablates, residual healthy thyroid tissue remaining after a thyroidectomy. We can also use I-131 therapy to monitor the progression, spread or recurrence of thyroid cancer.

How it works

Before I-131 therapy is administered, the patient usually undergoes surgery to remove the thyroid gland. After surgery, small amounts of thyroid tissue are often left behind. The surgeon does so to minimize damage to the recurrent laryngeal nerve (which controls the voice box) and the parathyroid glands (which control the body’s calcium levels).

After surgery, the patient follows preparation guidelines for the I-131 treatment. Preparation often includes increasing the TSH level, which stimulates the thyroid take up as much iodine as possible.

About six to eight weeks after surgery, and once the preparation is complete, we administer the I-131 therapy by mouth, in capsule form.

The iodine enters the bloodstream and concentrates in the thyroid gland, since thyroid cells take up iodine much more than any other cell in the body. Once there, the radioactive iodine destroys, or ablates, any residual thyroid tissue left behind, as well as thyroid cancer cells in lymph nodes or other parts of the body. After administering the I-131, we perform a whole body diagnostic scan to see where the iodine collects in the body.

We often provide I-131 therapy in combination with surgery and other treatments for thyroid cancer, such as hormone therapy.

Since radioactive iodine for thyroid cancer causes the body to give off radiation for a period of time, it requires special precautions to prevent exposure to other people.

Who is eligible?

I-131 therapy may be a treatment option for certain types of thyroid cancer depending on several factors, including the size of the original tumor, the number of sites involved, involvement of the borders of the thyroid or adjacent tissues, and evidence of metastasis. I-131 therapy is not used to treat medullary or anaplastic thyroid cancers, because these types of cancer cells do not take up iodine.

If I-131 is an appropriate treatment option for you, your care team will discuss the possible risks and benefits with you, as well as necessary precautions, to help you to make an informed decision.